The present invention relates to an optical record carrier such as an optical disc and an information recording/reproducing apparatus for the optical record carrier, and more particularly to an optical record carrier suited for performing a stable tracking operation and an information recording/reproducing apparatus for such an optical record carrier. Further, the present invention relates to a master disc cutting apparatus for forming a master disc suitable for mass producing a record carrier in which a guide groove, header pits, and a tracking-error detecting pit pattern are previously formed.
An apparatus for recording information in a land existing between adjacent pregrooves and for reproducing the recorded information is proposed in Japanese Patent Application Unexamined Publication No. 58-41446. In this apparatus, the deviation of a light spot from a track is detected by using a 3-spot tracking servo mechanism. However, the deviation of the light spot from a track can also be detected by a change in diffracted light pattern from the guide groove. In this case, there arises a problem that an offset occurs on the basis of a change in intensity distribution of diffracted light on a photodetector which is caused by the tilting of a record carrier, the movement of the light spot, or others. Means for reducing such a track offset is disclosed in, for example, Japanese Patent Application Unexamined Publication No. 59-19250 (corresponding to U.S. application Ser. No. 515,520 now U.S. Pat. No. 4,663,751, and EPC application Appln. No. 83107110.5).